The main objective of this study is to assess salivary cortisol at baseline and in response to low dose dexamethasone (DST) in hospitalized adolescents with a diagnosis of Post Traumatic Stress Disorder (PTSD) compared to: 1) hospitalized adolescents with histories of trauma who do not meet diagnostic criteria for PTSD; 2) a control group of healthy adolescents from a medical clinic serving the same community.